Organic light-emitting device using organic substances are categorized to a coated type and a vapor-deposited type, though both fail to have sufficient durability. One of the significant factors is water. When water exists in the light-emitting device, water is decomposed to oxygen and hydrogen by electrolysis, and the generation of oxygen and hydrogen deteriorates the durability of the light-emitting device. The reaction of water with a cathode also causes the deterioration of durability.
Proposed as a means for removing water is a dryer disposed in a sealing element (JP 9-148066 A). Though this means can remove water in an atmosphere, it fails to remove water in a substrate or an organic layer. JP 2002-8852 A proposes that an alkali or alkaline earth metal is disposed in a sealed space of the light-emitting device. However, these metals are unstable because of extremely high reactivity to water and oxygen, thereby failing to provide the light-emitting device with stable durability. Accordingly, it is strongly desired in this technical field to deprive the light-emitting device of a sealed space as much as possible and remove water from the device as completely as possible.